The invention concerns a method of circulation of a liquid phase through a solid phase, particularly for biocatalytical reactions performed for instance by means of immobilized enzymes and cells, and a device for realization thereof.
Some processes, particularly physical, chemical or biotechnological, require that a liquid should stream through a layer of porous, granular or similar material. It is known that layers of these materials substantially increase the area of contact between the liquid and the solid phase in the given volume of the appropriate device, thereby substantially accelerating the processes which arise as a consequence of interaction of the two phases.
Among the latter processes are physical adsorption, chemisorption, desorption, catalytical reactions (a carrier with an active layer), biocatalytical reactions, chromatography, ion exchange, etc.
Considerable importance has currently been gained by biological and biotechnological processes making use of the contact of a liquid phase with activated solid supports based on macroporous polymers and copolymers, hydrophilic pastes or gels, ion exchangers, which bear on their surfaces conjugated different biological materials.
In all these processes it is required that a liquid medium, for instance a fluid, should penetrate, leak, seep or stream through a layer of the solid support, during which process a desirable change occurs, usually an exchange or a change of some of the mass components between the fluid and the solid phase.
Biocatalysis is currently accomplished in a stirred batch reactor or in continuous reactors with stirred or fixed beds usually in columns. In both batch and continuous reactors the impeller is either anchor-shaped or paddle-wheel (screw-shaped or propeller-shaped paddles)
Biocatalysts are for the most part formed by amorphous (irregular) particles with size distribution 0.01 to 5 mm, and they are considerably damaged by the impact of the paddle-wheel agitators.
Continuous presence of biocatalyst particles in a stirred batch reactor is ensured for instance by a built-in filter septum at the bottom of the reactor above the outlet opening. After termination of the reaction the converted fluid is separated from the particles by filtration through said septum accomplished either by means of a vacuum (through the bottom of the reactor) or a pressure imposed on the surface of the fluid in the reactor. This filtration poses problems as it may cause clogging of the filter surface (pores in a textile material) and formation of a wet cake, and considerable pressure is necessary to remove the fluid from the reactor. Also, mechanical damage to the particles by the impeller during their repeated multiple use leads to the disintegration of larger particles to smaller ones which then clog the filter surface, limiting thereby its prolonged use.